Iraqi rescue workers inspect damages after a suicide bomb attack at the Shiite endowment headquarters in central Baghdad. (Photo by Ahmad Al-Rubaye/AFP/Getty Images)

From October 1980 to September 2015, according to a new paper by Benjamin Acosta, an assistant professor at Louisiana State University, 123 militant groups carried out 5,305 suicide attacks, killing more than 40,000 people. Just this year, suicide attacks have hit Afghanistan, Belgium, France, Indonesia, Iraq, Pakistan, Syria, and Turkey, among others.

A growing body of research suggests that suicide attacks often prevent groups from achieving their political goals. So why do groups keep using the tactic? Acosta analyzed a database of more than  5,000 suicide attacks to find out. “Organizations adopt suicide attacks to strengthen their support structures, extend their life spans, and boost or preserve status,” he found.

In a recent phone interview, Acosta discussed the motivations behind suicide attacks and what accounts for their popularity.

NL & SW: Is there an academic consensus on why militant groups carry out suicide attacks?

I’ve been working on this topic for more than a decade, and there hasn’t been a strong consensus. Post 9/11, the theory that emerged, inspired by Robert Pape, at the University of Chicago, was that foreign occupation was the cause of suicide attacks. For reasons probably related to ideology, journalists and academics accepted his theory, even though it had little empirical support.

But a bunch of studies that started emerging in 2005 and 2006 started to roll back the notion that foreign occupation was the driving motivation of suicide attacks.

NL & SW: So what is the driving motivation behind suicide attacks?

What’s really come into focus is that Islam and other cultures of martyrdom are a major causal component of the increase in suicide terrorism. These incentives are obvious at the individual level.

But what I’m interested in is why organizations continue to conduct suicide attacks. All organizations have two main goals: outcome goals, which are goals that relate to the purpose of the organization, and survival. Suicide attacks make it harder for groups to achieve their outcome goals. But they do make groups much more likely to survive.

NL & SW: How so?

Militant organizations go through different trends or fashions. Organizations must either adopt the fashion or become irrelevant. In the 1960s, the “international revolutionary” and the “urban guerrilla” were in fashion, and they preferred to rely on hijackings and hostage taking. As we’ve moved into the era of fundamentalist Islamist terrorism, organizations have had to adopt the fashions of fundamentalist Islam to stay relevant, and the key fashion is the suicide bomb.

If you’re a smaller organization like Ansar Bait al-Maqdis, and you want to draw the support and attention of the Islamic State and other groups, you start conducting suicide attacks. A few months after Ansar Bait al-Maqdis adopted suicide attacks, they were recognized as Wilayat Sinai, a province of the Islamic State, and they received funding and fighters from the core group, improving their survival prospects.

NL & SW: Has the Islamic State explicitly cited suicide attacks as grounds for supporting other groups?

Most of the time the group doesn’t mention it directly. But if you go back to the beginning of the Syrian civil war, when there were dozens of jihadi groups operating independently, it was the ones that adopted the suicide attack that gained attention from older and larger groups. Al-Qaeda, for example, soon sponsored al-Nusra. Was this solely because al-Nusra had adopted suicide attacks? It’s hard to say. But it certainly appeared to be a contributing factor.

NL & SW: But launching suicide attacks damages a group’s political prospects, right?

That’s right. There are two main ways that militant groups achieve outcome goals: first, through coercion, and second, through brute force. Either you coerce your target into giving you what you want, or you annihilate them. If militant organizations are fighting asymmetric conflicts, as they usually are, then the brute force option rarely works. So then they turn to coercion. For that to work, you need to pose a credible threat to other groups — but not so much of a threat that they don’t want to negotiate with you. This is a tough balancing act. Suicide attacks, because they are so inhumane, decrease your ability to win concessions at the negotiating table.

In the 1990s, for example, Palestinian terrorism finally brought the Israeli government to the table, but when the group later began launching suicide attacks, Israelis would say, “We have no negotiating partner anymore. They’ve proven that they’re willing to kill themselves to kill us. How can we then sit down and talk to them?”

NL & SW: So for terrorist groups, surviving is more important than achieving outcome goals?

Absolutely. These groups are trying to achieve really abstract, difficult, unlikely goals — establishing a caliphate, for instance. If you’re pursuing these hard goals, then your ability to fight the long war becomes more important. Even successful organizations like the Islamic State, which has established a caliphate in parts of the Levant and Iraq, are playing the long game. For them, this is a hundred years’ war, not something that will be concluded in the immediate future.

Sam Winter-Levy is staff editor at Foreign Affairs.

Nikita Lalwani is the former staff editor at Foreign Affairs.